Relay



P. L. S. LUM

March 24, 1936.

RELAY Filed March 27, 1934 2 Sheets-Sheet l MalCh 24, P. l s. LUM .Y vRELAY Filed March 27, 1954 2 Sheets-Sheel 2 ATTORNEY Patented Mar. 24,1936 UNITED STATES PATENT OFFICE RELAY Philip L. S. Lum, Chatham, N. J.,assignor to L. A. B. Corporation, Newark, N. J., a corporation of NewJersey This invention relates to improvements in relays and moreparticularly to devices of this character which are adapted to be usedin connection with alternating currents.

Polarized relays for direct current are very well known and in mostcases make use of a magnetized piece of steel or permanent magnet toobtain polarization.

I'here are also known certain types of polarized A. C. relays, most ofwhich however areadapted to only one special purpose and are verylimited in their usefulness.

An object of the invention is to provide an alternating current relaythat has extremely high sensitivity and which will respond to currentimpulses which are too weak to operate any ordinary relay. Anotherobject is to provide a relay which is adapted to discriminate betweencurrents of different signs; in other words, which will react in one wayif current flows in' one direction and which will react in a differentWay if the current flows in opposite direction. Generally such relaysare called polarized relays as polarization of certain parts of therelay is used to obtain the desired effect of sensitivity to currents ofdifferent signs. i

Other objects of this invention, not at this time more particularlyenumerated, will be clearly understood from the following detaileddescription of the same.

The invention is clearly illustrated in the ac-V companying drawings, inwhich:

Fig. 1 is a front elevation with certain parts in section showing apreferred form of relay embodying this invention; and Fig. 2 is a sideelevation of the same with some portions omitted and others in verticalsection.

Fig. 3 is a similar front'elevation, and Fig. 4 a similar sideelevation, with parts in section, but showing another form of relayaccording to this invention.

Fig. 5 shows a schematic circuit diagram of a i relay connected for use.Fig. 5 shows an arrangement of multiple contacts for relay and thecorresponding schematic circuit diagram, the

core and windings being omitted. Fig. 7 is a/ fragmentary side elevationof a portion of the structure of Fig. 6. Fig. 8 shows the same relayconnected for use as a differential polarized relay of insulatingmaterial such as bakelite, slate, marble, or the like, and 2 is a coreof magnetic material built up to the desired thickness preferably out ofinsulated laminations in a similar way as transformer cores areconstructed. The 5 laminations are held together by rivets 3 and thewhole core is mounted upon the base plate I by means of the screws 4 andspacers 5. Upon this core are mounted two coils 'I and 8 shown insection. 'Ihese two coils are electrically'connected 10 in series andtheir sense of winding is such that the fields created by each coil arein the same direction and therefore ladd up. The free terminals of thecoils I and 8 are connected respetively to terminal posts 9 and I0. 15

A clamp II is mounted on the core 2 by means of screw 6 and serves thepurpose of holding a thin spring steel hinge I2 which is connectedrigidly to the clamp II by means of screws I3. An armature I4 is rigidlyconnected to the free 20 end of the spring hinge I2 by means of rivetsI5, and can swing freely in the free space within the hollow core of thebobbin I6.' This bobbin is made of insulating material and is mountedrigidly on the core 2 by means of screws -I 'I 25 and I8. A pin I9 isfixedly inserted into the free end of the armature M and this pin isslotted at its free end. Into this slot is .inserted a nonmagneticspring leaf 20 that is riveted to the pin I9 or soldered to it. The freeend of this spring 30 leaf 20 is provided with a double sided contact 2Iwhich protrudes on both sides of the spring leaf. Adjacent to thiscontact 2|, but separated from it by an air gap, are two stationarycontact screws 22 and 23, each of which is mounted in a 35 threaded holeof the posts 24 and 25 respectively. The posts 24 and 25 are mounted onthe base plate I and are split at their outer end portions and throughthe axis of the threaded hole so that the contactscrews 22 and 23 willbe gripped, due 40 to the spring action of the two halves of the slottedposts and held safe against vibrations.

'I'he bobbin I6 carries one or more windings, the impedance of whichdepends on the purpose for which the relay is intended. If the source ofsupply for these windings is of high tension but of very small currentcapacity, the number of turns would be high and the diameter of the wireused very small so as to insure high impedance of the coil and highnumber of turns. If the supn ply, however, is of low voltage but ofrelatively high current capacity, a few turns of heavy wire would beused, Depending upon the purpose of the relay, whether itis to be usedas a simple polarized relay or as a differential polarized relay,

one or more coils can be used on bobbin I6. .I

, have shown two coils 32 and 33 as this' will provide the possibilityof using the relay in different combinations. These coils arehereinafter referrcd to as operating' coils. The ends of the coils arebrought to terminals 26, 21, 28, and 29 so as to be available foroutside connections. Terminal 30 has been connected with the metal frame2 of the relay. i

It will be understood that the armature I4 can move to the right and tothe left until the contact 2| touches either contact 22 or contact 23and that if further forces are acting onthe armature, the spring leaf 20by flexing will allow the armature to keep on moving until it is blockedby the insu# If now an alternating current is sent through the coils Iand 8 which are hereafter called the polarizing coils, an alternatingflux will be set up in the core 2 and in the air gap between the poleends 3| and 3 I The highest eld concentration will be directly betweenthe tips of the pole ends and will bulge out from their normal to theaxis of coils 'I and 8. It is obvious, therefore, that the free end ofthe armature I4 will be located in the bulging or extending part of themagnetic eld and that this field will exert a longitudinal pull upon thearmature, trying to pull it into the air gap between the poles 3| and3|', but without moving it sideways. That part of the pole ends 3| and3l which faces the armature is recessed cylindrically as shown and insuch a way that the armature I4 can never come into direct contact withthe core.

If now an A. C. ,of equal frequency and phase as the polarizing A. C. isintroduced into the operating coils 32 and 33 so as to magnetize thearmature I4, the armature will move sideways in a definite directiondepending upon the direction of flow of current in coils 32 and 33. Ifwe assume that both these coils are connected in series and so as to addup `their eect upon the armature I4, and if we further assume that tip3| at a given moment is a north pole while tip 1 3| at the same time isa south pole, and that the free end of the armature I4 at the same givenmoment assumes north polarity, then the armature will move toward thetip 3| under the influence of the two different magnetic fields cre- Yated by the two different currents.'

It is easily understood that the magnetic ux created in the armature bythe current through the coils 32 and 33 has to pass through the core 2in order to complete its path. Therefore, this ux will add to the fieldof coil I and subtract from the eld of coil 8, thereby unbalancing thecenter of pull of the main magnetic field between the tips 3l and 3`I'and shifting this center towards tip 3|. Inasmuch as during the nexthalf cycle all polarities in all coils change at the same time, thearmature will, during the next half cycle, be moved in the samedirection as in the rst half cycle. Its inertia will be suilicient toprevent it from snapping back into the zero position, provided thefrequency of the currents is high enough to make one-half cycle short ascompared to the mechanical time constant of the armature and spring.

Inasmuch, as during its motion the armature does not approach the tip 3|but stays substan` tially at the same distance therefrom, there would beno increase of the magnetic ux and no resulting acceleration to thearmature. This means that the armature will not snap over, but will movegradually and assume a definite point of rest, in which the force of theunbalanced or shiftedmagnetic field is equal to the restoring forces ofthe spring hinge I2. The eiect of the spring hinge I2 can be compensatedfor to any desired extent by shaping the pole ends 30 and 3| so thatthere is a slight decrease in the distance of the armature from thepoles the more the armature moves out. If this decrease is made too muchthe resulting increase in magnetic flux density will overcome therestoring forces of the spring entirely and the armature would ybeaccelerated from its normal position, resulting in a snap action of thearmature. The snap action of the armature results in quick motion butthe operating current through coils 32 and 33 would have to be decreasedconsiderably before the armature would snap back into its normalposition.

If, on the other hand, the shape of the pole ends 3D and 3| is such asto compensate for only part of the spring action, the position of thearmature will depend entirely upon the amount of current through thecoils 32 and 33, or the angular motion of the armature under theiniiuence of the operating current would beA a function of the sign aswell as the amplitude of the current, because it is easily understoodthat a reversal of the current through coils 32 and 33 u will move thearmature toward pole end 3|. the poles are shaped so that the free spacebetween the free end of the armature and the poles tends to increase,the motion of the armature under the influence of a rising operatingcurrent will be such that the armature will not move beyond a certainpoint, i. e. the point at which the increase of spring tension isgreater than the increase in total magnetic force. v

These characteristic actions of the relay can be used to advantage if itis desired to obtain from the relay indications not only of the sign ofthe iiow of current through the operating coil but also of the amount ofcurrent at any given moment. Fig. 6 shows how this can be done.

The armature I4 is designed the same way as rin Figs. 1 and 2 but thepin I9 carries five contact springs instead of only one, the leaf 2U.Spring leaves 34, 35, 36, and 31 have been added. 'Ihese spring leavesare all free at one end and spaced apart from each other and are allconnected together to the pin I9 at the other end.

Spring 20 as before carries a double sided contact 2| but the othersprings carry single contacts as shown. Opposed to each of the contactsare contact screws, so that the contact car-` ried by leaf 34 can makeconnection with contact screw 38; 35 with 39; 36 with 40; and 31 with4I. Contact screws 22 and 23 are in the same place as before but theyare now mounted in insulating pieces or brackets 42 and 43,respectively, together with the other contact screws. Split metalbushings 44 have been inserted into the insulating brackets 43 and 42and from each of these bushings extends a wire to provide for outsideconnections. The brackets 42 and 43 are mounted on the base plate I bymeans of screws 45.

The action of this multi-contact armature under the influence of arising operating current through coils 32 and 33 is now as follows: Ifwe assume that the direction of the operating current is such as tocause armature I4 to move to the left in Fig. 6, contact 2| will be thefirst to make contact with its adjacent screw 22,

aos-w01 while the contact on leaf will connect with contact screw 39after the armature has moved a little further. At that time both thecontacts 2| and 35 are engaged. If the current still continues to rise,the contact 34 would encounter contact 38 and all three contacts at thattime will be engaged together. If the operating current now graduallydecreases, contacts 38-34 will open rst, then contacts 39-35 and thencontacts 22-2I. As soon as the operating current reaches zero, thearmature will be in its normal position and if the operating current nowreverses its sign and increases again, the same procedure to the rightof Fig. 6 will take place in similar sequence.

Irrespective of the number of contacts upon the armature, it should beunderstood that, having an armature which moves to a certain extentproportional to the sign at the amplitude of an operating current, theresponse of the armature will be immediate upon the change of the amountof current. As explained before, the pole ends could be shaped so that`the armature would move with a snap or with acceleration resulting inquick make and break, but appreciable changes of current would benecessary to move the armature out of its once assumed position. Iteither would go the full way or not at all, and after it has gone thefull way the current would have to be reduced considerably in order toallow the spring to move the 'armature back. However, with the armaturemoving nearly prov portional to the current a snap action is impossibleand the armature will respond immediately, and this response will be afunction of the amount and direction of the current.

Figs. 3 and 4 show another preferred form oi the relay. In al1essentials except the armature it is constructed as that shown in Figs.l and 2. The armature 46 is not hinged to the core 2 as before butpivoted as shown. The

laminations of the core 2 extend .all the way through the operatingcoils 41 and 48 in the shape of an extension 49. Two flat metal stripsor plates 50 and 5| are shaped so as to extend slightly beyond the coreV49 and carry atA their extreme end two y"screws 52 and 53 respectively.'I'hese screws are held against rotation by means of check nuts 54 and56 and extend beyond the plates 5| and 50. Their inner ends are hard-`ened and countersunk and between these two points swings the armature 46which is fastened to the needle point pivot 55. If correctly adjustedsuch bearings have substantially the least possible friction of allknown bearings and pro- .vide a very satisfactory means of attaching thevarmature 46 to the core 49. Due to the comparatively largecross-section of the core 49 a 'rather high magnetic fiuxcan begenerated in the armature by a comparatively weak alternating currentthrough the coils 41 and 48. A- pin 51 is inserted into the free end ofarmature 46 andcarries a spring leaf contact 58 which is similar asdescribed for Fig. 1 and Fig. 2. There is no mechanical centralizingforce on the'armature 46, as there is no spring hinge and no otherrestoring spring. The centralizing force for this armature is providedfor bythe magnetic field between vthe pole ends 3| and 3|', which areshaped so that in its normal or zero position the end of the armature isnearest to the pole ends but sufficiently far away from both to beI onlyunder the influence of that part of the field which bulges out andcurves away from the pole tips. If this were not the case the `armaturecoils, while the midpoint would try to assume a position either nearestto one or the other pole tip and would not have a normal zero position.The poles are shaped so that the distance of the free end of thearmature from the poles increases with increasing angle of motion. Incase of operating currents of varying amplitude the armature will followthe shift of maximum pull of the polarizing field and its angular motionwill be proportional to the sign and the amplitude of the operatingcurrent. This type of relay also can be provided with multiple contactsas shown in Fig. 6.

It is also possible to construct a relay of the above describedcharacteristics by using separate cores for the different magneticcircuits and by connecting these cores in such a way, that the ux willbe conducted to the desired points. Such a relay is shown in Figs. 9 and10. The polarizing coils'96 and 97 are mounted on pole pieces 98 and 99,which in turn are riveted to the U-shaped steel yoke or core frame |00.The operating coil |0i is mounted on the same core frame |00 which framein effect becomes an extension of core 98-99. The armature |02 issuspended substantially midway of its length between pivot screws H3 andH4 and can swing within the hollow operating coil |0l. If this armaturel0? and the spring leaf contact H5 carried thereby are suspended so thatthe same is completely balanced, the assembly will be substantiallyvibration-proof,

The contacts are arranged at that end of the armature, which is notinfluenced by the polarizing coils, but their action is identical withthose of the aforedescribed relays. Terminals |03, |04, |05, |06, |01,and |08 are provided and fastened to the base |09, which is made ofinsulated material. Terminals |03 and |06 serve the polarizing coils,and terminals |04 and |07 serve the single operating coil, but theirwire connections are concealed in the base and not shown. Terminals |05and |08 are fastened to the contact carriers ||0 and and serve for thesecondary circuit. The frame |00 serves as the electr'cal connection forthe center Contact on the arma'- ture and a wire may be fastened underthe nut ||2 holding this .frame to base |09. This type of relay also maybe provided with multiple contacts as shown in Figs. 6 and 7. Although,only one operating coil is shown in Figs. 9 and 10, as anyone skilled inthe art will readily see, two lsuch coils could be wound on the samebobbin, if desired.

Fig. 5 shows one of the many possible uses for the polarized relay.- Ina diagrammatic way the solid iron core of the relay is shown as a solidline 59 and the armature is shown at E0.. 6| and 62 are the polarizingcoils and 63 and 64 are the operating coils. As shown in the diagram, anA. C. supply is represented by the two lines 65 and 66. The polarizingcoils 6| and 62 are energized from the supply through a. variableresistance 61, the purpose of which is to vary the iield strength in theair-gap in order to obtain perfect balance of the magnet'c circuits. Theoperating coils 63 and 64 are shown as connected in series so that theirrespective elds are adding up. The slider of a potentiometer 69 isconnected to one free terminal of the operating 'l0 of the samepotentiometer is connected to the other free' terminal of the operatingcoils. 'Ihe potentiometer itself is energized from the supply lines 65and 66. In the position shown, where the slider 68 is directly on themidpoint l0 of the potentiometer,

no current is flowing through the operating coils. Therefore, theamature will remain in its neutral position.

If now the slider 68 is moved slightly toward one side of 'thepotentiometer, a current will flow in a certain direction through theoperating coils and thereby cause the armature to leave its centralposition. If we assume that the polarities of the polarizing and theoperating coils are such that the armature will move toward the left,contact 1I will connect with contact 12. 'This will close a secondarycircuit which goes from the negative terminal of battery 19 through theamature 89 and the contact spring, through contacts 1I and 12 and fromthere to the lamp 15 from where the circuit is closed by the return wireto positive terminal of battery 19. Lamp 15 will glow as long ascontacts 1l and 12 are touching. If the slider 68 is moved further outin the same direction as before, the` current through coils 63 and 89will increase and the armature will try to move further to the left.This will ex the contact spring and contact 1I will slide slightly overcontact 12. By reversing the motion of the slider it will graduallyapproach again point 10 and at this point the armaturewill have brokenthe contact and be back at its neutral position. Continuation of themotion of the slider in this direction, which means toward the otherside of center point 18, Will reverse the direction of ow o currentthrough the operating coils and thereby move the amature now to vtheright. At a certain position of the slider 68 the armature will havemoved far enough to make contact 1I touch contact 13 whereby the lamp 16is lighted. i

It is, therefore, possible by means of this relay, to indicate at aremote point the motion of the slider 68 with respect to the centerpoint 10 on the potentiometer 89. The slider may be connected to animportant operating part of some industrial installation, for instance avalve or a float on the surface of some liquid or anything whichnormally has a neutral position. Any departure from this neutralposition would be indicated at any` given remote point by the lights I5and 16 which naturally could also be duplicated by parallel lights so asto have indications at diierent points.

The possibilities of uses for the proportional motion of the armaturewith respect to the amount of current flowing through the operatingcoils can be best demonstrated by Fig. 6 which contains also a schematicwiring diagram for the use of this relay to control a number of remoteindicating lamps. These lamps are used in a similar manner as shown inFig. 5, but instead of having one lamp for each direction of current inthe operating coils, three lamps for each direction are used here insuch a manner, that the number of lights burning simultaneously denotethe quant'ty of current flowing. The electrical connections for thecoils of the relay proper are identical with those shown in Fig. 5. Butinstead ofA using but one lamp 18 in Fig. 7, there are three lamps 89,8l, and 82 in Fig. 6, and for lamp 15 in Fig. 5 there are substitutedthree lamps 11, 18, and 19 in Fig. 6,. Lamps 88, 8l, and 92 are shownconnected to contact screws 23, 48, and 4 I while the lamps 11, 18, and19 are respectively connected to contact screws 22, 39 and 38.

The electrical connections of the relay itself, the major part not beingshown in Fig. 6, are, as mentioned, identical with those of Fig. 5. Itwill be clearlv understood that if the armature is un- Yterminal of thebattery aolsavoi der the inuence of a slowly rising control voltagecaused by motion of a slider similar to slider 88 in Fig. 5, whichvoltage tends to move the armature in Fig. 6 toward the left, thatcontact 2l will be.

the i'lrst to make connection with contact 22 and at that time start acurrent to flow from the negative terminal of battery 83 through thearmature and the contact spring 28, through contacts 2i and 22, throughlamp 11 and from there through the common connection 89 back to thepositive 83. If the current through the operating coils of the relayfurther increases, the armature will move further to the left and causecontact spring 35 to make contact with the screw 39, thereby energizinglamp 18 also. Both lamps 11 and 18 are now glowing. Further increase ofthe operating current will move the armature I9 still further to theleft until contact spring 38 connects with contact screw 38 and therebylights also lamp 19. Gradual decrease of the current through theoperating coils of the relay will move armature I 4 back toward itsneutral position and first open the contact between 38 and 38, then thecontact between 35 and 39, eachtime extinguishing one lamp. Finally thecontact between 2 land 22 will be brokenv and all lamps will be out.

If now the current through the operating coils isreversed by moving theslider similar to slider 68 in Fig. 5 beyond the center point towardsthe other end of the potentiometer 89 and starts to increase from zeroin the opposite direction, the armature I4 will move toward the rightand consecutively close the three contacts associated with the screws23, 40 and 4I. 'I'his in turn will consecutively energize lamps 80, 8|,and 82, so that finally all three lamps are lighted. It is thereforepossible, by means of the polarized relay, to indicate at a remote pointthe position of the slider 68, at least in so far as the six lamps willshow definitely, that the slider has reached lor passed a vcertainpoint. Anybody skilled in the art can imagine the numerous possibilitiesof connecting the control slider 68 with some important manipulationwhich has to be watched or known.

As shown in Fig. 8, which again shows a schematic wiring diagram of therelay, it also can be used as a dilerential polarized relay. In thiscase the operating coils 63 and 64 are connected in such a way thattheir fields oppose each other. If the total number of ampere turns andthe impedance of the coils are identical, no' magnetization of thearma-ture will result as long as the currents owing through each coilare equal in amplitude and opposite in direction of ow. As shown in Fig.8, the common connection between coils 63 and 84 is connected to line 65of the A. C.

supply. 'Ihe free end of coil 64 is connected to the control slider 89on potentiometer 98, while the free terminal of coil 83 is connected tothe slider 92 on potentiometer 93. Both potentiometers are energizedfrom the common A. C. supply 66 and 69. As long as the sliders 89 and 92are positioned so that the potential between slider 89 and point 94 isequal to that between slider 92 and point 99, the currents through coil63`and `coil 84 will be equal and opposite and their eiect on thearmature will be zero. If slider 89 is now moved toward the terminal 95of potentiometer. 90, the current through coil 64 will decrease whilethe current through coil 63 stays constant. In

y coil.

the more the armature would be moved out of its central position towardone side. Reversal of the motion of slider 89 will bring the amatureback progressively toward the neutral point, and as soon as thepotential between 89 and 94 becomes again equal to that between 92 and94, the armature will have reached its zero position. If the slider 99is now moved toward the terminal 96 of potentiometer 90, the armaturewould be moved off its neutral point toward the other side. Motion ofthe slider 92 would have a similar eect. The secondary circuit,controlled by the contacts ll, 12, and '13, could be similar to that inFig. 5, and therefore is omitted in Fig. 8. 'I'his relay also could beequipped with multiple contacts, as shown in Fig. 6.

From the foregoing description of the secondary circuits of the relay itis obvious how the differential relay also could be used to controllights or other apparatus or any other suitable instruments which it isdesired to control by means of the motion of the sliders 89 and 92. Itis obvious, however, that the differential polarized relay allows thecomparison between two A. C. currents or different sources but of equalfrequency and phase and to find whether the current to be compared ishigher or lower than the standard of comparison and to actuate from therelay means to indicate. directly or indirectly such differences.

It is also evident, that the relay of Fig. 5 will vrespond to a changeof phase between the current in the operating and the current in thepolarizing coils. If the phase angle is the armature of the relay willbe in its neutral position, or very near that position. If the phaseangle is either zero or the armature will be at one or the other extremeend of its possible sweep. Angles of phase in between the just mentionedangles will result in intermediate positions of the armature, whichtherefore could be used as a phase angle indicator, so that it couldsignal any departure of the 90 phase angle of one current againstanother current, if such a problem should come up.

'I'he relay in Fig. 8 could serve a similar purpose, by signalling thechange of the phase angle of the current in one operating coilagainst'the phase angle of the current in the other operating As thearmature in Fig. 8 will be at its neutral position only, if the twocurrents are of opposite phase, any change of the phase angle of one o fthe currents would immediately actuate the relay. 'I'his can be utilizedwhere it is important to watch the power factor of an important circuit.

It is also evident that the functions of the operating coils and thepolarizing coils can be exchanged without materially changing thecharacteristic action of my relay.

II oneconsiders direct current as a special case of alternating current,namely as an alternating current with zero frequency, it becomesevident, that the above described relay, will be universally adapted forall types of current, without any change of their operatingcharacteristics.

As manyv changes could be mad'e in the above construction and manyapparently widely different embodiments of this invention could be madewithoutk departing from the scope thereof, as defined by the followingclaims, it is intended that all matter contained in the abovedescription or shown in the accompanying' drawings shall be interpretedas illustrative and not in a limiting sense.

I claim:

1. In a relay, a core having an airgap, means to maintain a magneticfield of selected fixed average value in and around said airgap, anarmature mounted on said core and adapted to move entirely exteriorly ofbut adjacent to said core airgap and to be normally held in a centralposition, means to produce in said armature a magnetic eld variable asto sign and intensity so as to cause motion of 4said armature from itscentral position, said motion being proportional to the signrelationship of said last named field to that of the core eld and to afunction of the intensity of said armature field.

2. In a relay, comprising a core having pole extensions providing anairgap therebetween, polarizing windings on said core, a source ofpotential energizing said windings to maintain a magnetic eld ofselected fixed average value in and adjacent vto said core airgap, amovable armature mounted on said core having its free end adapted tomove entirely exteriorly of but adjacent to said airgap and to beinfluenced by said field so as to assume a normally central positionclose to the point of highest field intensity, operating windings toindependently magnetize said armature from. a source of supply havingsubstantially the same phaseand frequency as said first named source,means to vary the magnetizing current through said operating windings toproduce in said armature mechanical reactions proportional to the signof said current and to a function of its amplitude.

3. A relay comprising a core and a movable armature mounted on saidcore, said core having an airgap adjacent and normal to one movable endof said armature, said armature being positioned exteriorly of saidairgap and never entering the same polarizing windings on said coreenergized from a current supply to produce a magnetic 'iield in andadjacent to said airgap, operating windings independently energized fromsaid supply to magnetize said armature7 means to vary the currentthrough said operating coils as to sign and value to produce mechanicalmotion of said armature substantially proportional to the sign and thevalue of said current, and a plurality of contact means associated withsaid armature, certain of said contact means being carried by saidarmature and adapted to cooperate with others of said contact meansarrangedso as to be engaged successively depending upon the extent ofmotion of said armature, and adapted to operate secondary circuit means.

4. A relay, comprising a core having an airgap between two poleextensions thereof, an armature movably mounted on said core and adaptedto move entirely exteriorly of and adjacent to said airgap, polarizingwindings on said core, operating windings surrounding but notobstructing said armature, means independently associated with each ofsaid windings to impress thereon polarizing and operating potentials ofsubstantially equal phaseand frequency to produce in the armaturereactions substantially proportional to the sign and the amplitude ofsaid operating potential, a plurality of fixed contacts, and a pluralityof contacts associated with said armature and adapted to successivelyengage with said plurality of fixed contacts arranged on either side ofsaid armature, said contacts being ,adapted to operate secondary circuitmeans.

5. In a relay of the character described, core means having an airgaptherein, a winding on said core means adapted to be energized so as toestablish an alternating magnetic field within said airgap, an armatureassociated with said core means having a portion disposed to moveadjacent to but outside of said airgap, said armature never entring saidairgap, said armature being normally held in a neutral position by themagnetic field in said airgap, and winding means surrounding saidarmature and adapted for producing alternating flux therein to therebycause said armature to depart from its neutral position.

6. In a relay of the character described, a core having an airgaptherein, winding means on said core adapted to receive alternatingcurrent for establishing an alternating magnetic field of selected fixedaverage value in said airgap, an armature arranged to move adjacent tobut outside of said airgap so as never to enter the same, said armature'being normally held in a plane extending substantially at right anglesto said airgap and midway of the width thereof, and windingA meanssurrounding said armature and adapted to be supplied with alternatingcurrent, said armature being electromagnetically associated with saidcore whereby i'lux set up in said armature by said last named windingmeans will pass through a portion t of said core, thereby causing saidarmature to move from its normal position, the extent of movement of thearmature from its normal position depending upon the characteristics ofthe current passing through said last named windingmeans.

7. In a relay of the character described, a core having an airgaptherein, winding means on saidcore adapted to receive alternatingcurrent for establishing an alternating magnetic field of selected iixedaverage value in said airgap, an armature arranged to move adjacent tobut outside of said airgap so as never to enter the same, said armaturebeing normally held in a plane extending substantially at right anglesto said airgap and midway of the Width thereof, winding meanssurrounding said armature and adapted to be supplied with alternatingcurrent, said armature being electromagnetically associated with saidcore whereby flux set up insaid armature by said last named windingmeans will pass through a portion of said core, thereby causing saidarmature to move from its normal position, the extent of movement of thearmature from its normal position depending upon the characteristics ofthe current passing through said last named winding means, contact meanscarried by and movable with said armature, and stationary contactspositioned for selective engagement by said movable contact means.

8. In a relay of the character described, core means provided with anairgap therein, a winding on saidcore means adapted to be supplied withyalternating current for establishing an alternating magnetic eld ofsubstantially constant average value in said airgap, an armature movablyassociated with said core means and arranged to have one end movableadjacent but outside of said airgap so as never to enter the same, saidarmature being normally held by said field in a plane extending at rightangles to said eld and substantially midway of the width of said airgap,winding means surrounding said armature and adapted to be supplied withalternating current,

said armature being electromagnetically associated with said core means,whereby flux set up in said armature by alternating current passingthrough said winding means will extend within said core means, said fluxcooperating with the iiux set up by said core means winding, when anappreciable component of the current passing through said winding meansis in phase with the current passing through said core -means winding,to cause movement of said armature from its normal position, the extentof movement of said armature being a measure of such current component.t

9. In a relay of the character described, core means provided with anairgap therein, a winding on said core means adapted to be supplied withalternating current for establishing an alternating magnetic i-leld ofsubstantially constant average value in said airgap, an armature pivotedsubstantially at its center of gravity upon said core means and arrangedto have one end thereof movable adjacent but outside of said airgap,said armature never entering said airgap, contact means carried by theother end of said armature, stationary contact means for cooperatingwith said armature contact means, said armature being normally held bysaid eld in a plane extending at right angles to 'said field andsubstantially midway of the width of said airgap, winding meanssurrounding said armature and adapted to be supplied with alternatingcurrent, said armature being electromagnetically associated with saidcore means, whereby ux set up in said armature 10. In a relay of thecharacter described, core means having an airgap therein, winding meanson said core means adapted to be energized by alternating current forestablishing an alternating magnetic eld of substantially constantaverage value in said airgap, an armature movably associated with anextension of said core means and arranged to have one end movableadjacent but outside of said airgap so as not to enter the same, andnormally held by said field in a plane extending at right angles to saidfield substantially midway of the width of said airgap, winding meanssurrounding said armature and adapted to be supplied with alternatingcurrent, the phase of which is normally in quadrature with the phase ofsaid first named alternating current, so that departure of the phaserelations of said currents from quadrature will cause said armature tomove from its normal position and to assume a new position dependingupon the amount of change of phase angle between said

